Microwave ovens have been constructed in which the door periphery and adjacent oven wall portions are shaped to form a microwave energy seal for preventing the emission of microwave energy from inside the oven to the regions adjacent the outside of the oven. Such seals have generally been formed with a quarter wave choke structure which resonates at the frequency of the microwave energy supplied to the interior of the oven and cooperates with other portions of the seal structure to inhibit the transmission of microwave energy from the interior of the oven through a transmission structure formed by the spaced metal conductors of the oven wall and the metal conductors of the oven door. Such spacings have generally been found desirable either separated by air or by solid dielectrics to prevent arcing between the metal of the door and the metal of the oven wall at points where microwave energy field concentrations exceed the breakdown voltage of air or cooking vapors escaping from the oven. Such doors have structural members formed of materials such as stainless steel or aluminum which have low losses at microwave frequencies, and the microwave characteristics of the choke and other portions of the seal structure do not change dimensionally with time due to corrosion or other factors.
In the case of stainless steel structures, these were constructed by welding together several substantially planar members which had been partially deformed to form the sides of a door and then welding a stainless steel sheet containing door apertures and extensions beyond the periphery of the door which could be deformed to form portions of a choke seal. Such welding to form an accurate door which would for production purposes fit into any one of a number of ovens made to production tolerances requires jigging and piece alignment which is expensive as well as requiring the use of relatively expensive stainless steel sheet material. Cast aluminum door structures require relatively expensive aluminum castings and mold structures. In addition, such cast structures cannot be readily changed during production to meet changes in tolerances encountered due to wear of jigs and fixtures or changes in material specifications.